The power of suggestion can be an incredible thing, and in few way is this more apparent than with the placebo effect. Now, newly published research suggests how susceptible you are to sham treatments and dummy medicine (a sugar pill, for instance) could actually be rooted in your genetics.

Differences in versions of the catechol-O-methyltransferase (COMT) gene, which determines levels of dopamine in the brain's prefrontal cortex, are linked to differences in reward-seeking and pain perception. People with the high-dopamine version, or allele, of the COMT gene feel pain more acutely and seek rewards more strongly than those who have the low-dopamine copy.

[Researchers led by Kathryn Hall of Beth Israel Deaconess Medical Center] analyzed DNA from 104 patients with irritable bowel syndrome who were randomized to one of three groups: One was told they were on the waiting list for treatment, another received a placebo in the form of seemingly real, curt acupuncture, and the third group received fake acupuncture from a caring, warm practitioner who looked patients in the eye, asked about their progress, and even touched them lightly.

Patients with the high-dopamine version of the gene felt slightly better after seeing the curt, all-business health-care provider that gave placebo acupuncture. But they were six times as likely to say their symptoms improved with a caring practitioner as those with the low-dopamine gene, who didn't improve much in any group.

In the latest issue of PLOS ONE, Hall and her colleagues note that knowing if a person is genetically predisposed to respond favorably to a sham form of treatment could prove invaluable in clinical trials designed to test the effectiveness of drugs and other therapies. After all, if everyone in your placebo group is hardwired to respond favorably to any treatment — even to a sugar pill — it could seriously skew experimental results. Conversely, if the entire placebo group is genetically predisposed to not respond to placebos, it could cast the prospective therapy in a disproportionately favorable light.